There are many methods of treating wounds known to those skilled in the art. For example, skin grafting techniques exist which aim to reconstruct the skin covering areas of the body where there is either damage or defects to the skin. In general, these types of grafts are classified according to their host-donor relationship and by their thickness. The most clinically applied graft is the autologous graft, whereby tissue is taken from one area of the body and applied to another area. The grafted tissue then develops a new blood supply and attaches to the underlying tissues.
There are several types of skin grafts presently used, including split-thickness, full-thickness grafts, and micro-grafting. Each of these graft types must be prepared using certain techniques, and each one has its inherent advantages and disadvantages. Split-thickness grafts often require considerable skill, time and expensive equipment to perform. Further, donor sites are painful, result in scarring and limit the area able to be covered. Although they may be more successful than full-thickness grafts, they are usually less cosmetically attractive. Full-thickness grafts require less skill or expensive equipment, and their cosmetic appearance is better than that of split-thickness grafts. However, full-thickness grafts do not “take” as well as split-thickness grafts. Micro-grafts are more easily accomplished and require no special instruments. However, their cosmetic appearance is not as good as other techniques, as the resulting scarring is unacceptable.
A variation to the above grafting techniques is the mesh graft, which is a type of split-thickness or full-thickness skin graft in which parallel rows of slits are cut in the tissue being treated. Some of the advantages of mesh grafts include: a greater coverage of the effected area, drainage of blood or serum from under the graft, and increased conformity of the graft to uneven recipient areas. This technique has been very successful, with 90 to 100 percent “take” when the grafts have been applied on healthy granulation beds.
An alternative to split-skin grafting is to form a blister under suction at a donor site and transplant to the recipient site. The production of blisters to treat wounds has been used since the 1960s. The blisters are produced by a suction device, such as Dermavac™, at a suction pressure of approximately 250-300 mmHg for 1-2 hours. The blisters are then cut off and placed on the wound. The healing time is around 10-14 days. There are several disadvantages of this method such as the amount of time required to prepare the graft is too long and the graft may not result in re-pigmentation of the area; or uneven pigmentation is common around the edges of the area of treatment.
Micro-grafting has become a more common approach for large area cover and involves the “snipping off” of a number of very small sections of tissue from a donor site and applying then to a dressing, which is in turn applied to the wound area.
The most advanced technology for the generation of a tissue in vitro is to culture epidermis. Cultured epithelial autografts (CEA) are an important adjunct in the coverage of burns and other situations in which large areas of the body's surface experience skin loss. There are many centers throughout the world with tissue culture facilities whose aim is to produce autologous epithelial grafts for use in a wide variety of applications. The usefulness and application of CEA is related to its ability to achieve confluent cells sheets suitable for grafting. This technique overcomes many of the disadvantages of the previous treatments described above. For example, cultured epithelial autografts reduce the demand for donor sites. However, these autografts are slow growing and require time for culturing of the grafts, which often exceeds the time of preparation of the recipient's sites.
The present invention provides a cellular suspension together with a method for preparing that suspension and a device for its preparation each of which seek to ameliorate one or more of the disadvantages associated with prior art grafting technology.